The present invention relates to increasing performance of Wide Area Network (WAN) communications and in particular to a device positioned at both ends of a constrained link that reroutes outgoing packets to a proxy application that implements data compression.
The growth in data communication traffic, including email, client/server applications, multimedia applications, Internet and intranet applications, has continued to cause critical bandwidth shortages across many networks. This demand for instant data communication often exceeds the amount of bandwidth available, resulting in congestion and delay. As more applications move from Local Area Networks (LANs) to Wide Area Networks (WANs) application performance and response time issues become critical to continued smooth operation of an enterprise. With offices widely distributed around the globe and present day budgetary constraints, the implementation of additional wide area links is cost prohibitive for many international installations. Consequently, application and network architects need additional solutions to help them efficiently use existing bandwidth to support more applications and more end users.
The Open Systems Interconnection (OSI) reference model is a widely used model describing the flow of data traffic across a network. The OSI model has seven layers; each of the seven layers communicates with a layer below it through a specific interface and its peer layer on a different system in the network through a specific protocol. The combination of all networking protocol layers is often referred to as the networking stack. Packet based Transmission Control Protocol over Internet Protocol (TCP/IP) is perhaps the most widely known protocol in use in the Internet. IP is a network layer (Layer 3) protocol that defines a set of standards for addressing and routing of packets across a connectionless network. TCP is a connection oriented, transport layer (Layer 4) protocol that defines a way to ensure reliable transport of information.
Encoding or compression of network communication data is a natural choice of reducing the amount of traffic needed to be carried over a network link. Different schemes have been previously proposed for reducing traffic via compression. Most of these implementations concentrate on compressing traffic at the IP layer (Layer 3) of the OSI model. These Layer 3 encoding techniques are typically based on intra-packet and/or inter-packet compression schemes that have been described in the prior art. The aim of these schemes is to reduce the number of bytes transmitted in every packet; thus, these systems encode each packet or datagram independently, based upon information within each packet. Since they are not capable of detecting repetition of entire packets or repetitions that exist across multiple packets, they typically may miss many possible repetitions and therefore do not yield a high degree of reduction.
It is also well known to compress data at a much higher layer of the communications networking stack, such as at the application layer (Layer 7). For instance, images can be compressed in a variety of formats such as the Graphics Interchange Format (.gil) or the Joint Photographic Experts Group format (.jpeg). These data file-encoding formats reduce the space required for storage for such an image as well as its transmission. Hence, at the application layer a server may encode all of its images in the (.gif) format before transmission to a client on the other end of a WAN connection. Each image received by the client would then be decoded at the application layer to generate the original viewable image.
However, this form of application layer encoding and/or compression is typically performed offline, on single objects, prior to transmission. Such application layer encoding is not performed in an online fashion within a continuous communications stream. These types of encoding schemes are thus largely based only on intra-object information, that is, information contained in a single image, rather than inter-object information that consider data from all of the different objects to be transmitted from one or more servers to one or more clients.
For example, International Patent Publication Number WO 01/37516 describes a technique whereby a private network connection is implemented between devices known as accelerator exchange servers. A corresponding accelerator exchange client software is installed at a client's. The accelerator exchange client software may be implemented as a browser program adds on, for example.
U.S. Pat. No. 5,657,452 also discloses a method for setting up a connection over a data network. A proxy engine is used to implement data compression. However, this approach requires installation of the proxy engine so that it runs in a local endpoint node application.